Rep. Michael Capuano (D-Mass.) will not run for governor in 2014, he announced Thursday, putting an end to months of speculation that the Democrat might make a bid for higher office.

"After taking time to reflect with my family, I have decided that I will not be a candidate for Governor in 2014," he said in a statement. "I am truly touched by the support and encouragement I received throughout this process, but believe that I can best serve the Commonwealth in Congress. I will continue to be a strong voice for progressive policies in Washington."

Capuano was viewed as a top-tier potential candidate. His decision not to run only reaffirms that Attorney General Martha Coakley is the early front-runner on the Democratic side.

Also competing for the Democratic nod: Former Boston Globe columnist and Obama administration homeland security official Juliette Kayyem; former administrator for the Centers for Medicare and Medicaid Services Donald M. Berwick; state Treasurer Steven Grossman; state Sen. Daniel A. Wolf, and biotech executive and physician Joseph Avellone.

The presumptive Republican nominee in the open race is businessman Charlie Baker, who lost to Gov. Deval Patrick (D) in 2010.